1. Field of the Invention
The invention is related to the field of the polishing of lenses.
It relates in particular to an improved device for polishing lenses.
In the manufacture of spectacle lenses, the polishing is particularly important. The aim is to obtain, on the one hand, a sufficient finish quality, in order to obtain an optical polish so as to achieve the transparency of the lens, or to eliminate defects in the surface condition during the preceding machining operation referred to as generation. The aim is, on the other hand, to achieve as accurately as possible the prescribed radii of curvature, so that the effective correction corresponds to the recommended correction, without deformation of the surface that has been generated.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
A current system consists in laying the lens on a deformable (foam) surface and in causing the tool to evolve on the surface to be polished while causing the lens to rotate on itself. This results into a deformation of the support of the lens according to the shape of the lens itself, which means that depending on the place where one is located, the tool will more or less press the lens and therefore the polishing function will be different from one point to another, which results into a deformation.
US-2005/0221721 provides a device for polishing lenses, wherein the polishing tool is mounted on a tool holder secured to the end of a movable shaft rotating about its axis and movable in translation along its axis. The tool holder is in addition movable in rotation about a vertical axis passing close to the tool holder. As to the lens, it is held on a holding block secured to the end of a shaft movable in rotation about its axis, and in translation along its axis. This holding block is in addition movable in translation along a perpendicular horizontal axis. All these possibilities of movement permit any freedom of positioning the tool relative to the lens.
Nevertheless, the polishing is not regular enough, since the resting force of the tool on the lens is not identical in all positions.